In general, modern high-speed fiber optic communications systems are able to achieve high bandwidth by simultaneously transmitting data on multiple light beams of different wavelengths, over the same optical fiber. To do this, it is necessary for the light beams to be somehow combined (i.e. multiplexed) onto an optical fiber for transmission. Also, the reception of the data requires the different light beams be somehow separated (i.e. demultiplexed).
Presently, there are basically two different types of wavelength division multiplexing systems that are being used. These are: Coarse Wavelength Division Multiplexing (CWDM), and Dense Wavelength Division Multiplexing (DWDM). The main difference between these two types of systems is that DWDM can handle more channels of communications than can CWDM. A consequence of this, however, is that CWDM requires less wavelength control than does DWDM and, thus, can be less expensive. Regardless which type system is being used, each transmitted light beam originates at a laser source that is tuned to a predetermined wavelength. This light beam is then received at a detector that is dedicated to the predetermined wavelength. In practice, the tuned laser source and the detector are often combined in the same device. This device both modulates data onto the laser light beam, and demodulates the data from the detector. One such device which is useful for high-speed operation, and which is well known in the pertinent art, is a GigaBit Interface Converter (GBIC).
Heretofore, multiplexers and demultiplexers have been manufactured to handle a predetermined number of different wavelength light beams (e.g. sixteen) in a fiber optic communications system. Accordingly, a communications terminal in the system that is intended to service sixteen, or fewer, channels would require one multiplexer and one demultiplexer. The multiplexes are typically housed in a separate shelf that is dedicated for passive components. In this case, the multiplexer would be connected via patchcord cables directly to as many individual GBIC's as there are light beam communications channels being serviced by the system. Likewise the demultiplexer would be connected via patchcord cables directly to these same GBIC's. This would be the case, even though less than the potential sixteen channels are being used (e.g. only five light beam communication channels in use). In other words, only cables corresponding to existing GBICS (interfaces) are in place. Additional GBICS (interfaces) require additional cabling that will be most likely between the GBIC (interface) and a specific port of the modulator/demodulator.
In light of the above, it is an object of the present invention to provide a modular, stand-alone optical add/drop (OAD) device that can be used in a fiber optic communications system and plugs directly into an interface converter on the networking equipment to thereby eliminate exhaustive cabling, and reduce the possibility of miscabling. Another object of the present invention is to provide an OAD device that plugs into a GBIC for transmitting and receiving communications light beams having a predetermined wavelength. Yet another object of the present invention is to provide an OAD device that can be connected in series with other OAD devices to establish an “n” number of direct connections to a corresponding number of GBIC's. Another object of the present invention is to provide an OAD device that is relatively easy to manufacture, is easy to use, and is comparatively cost effective.